Two-electron Oxidation Of Water Research Articles

Stable production of hydrogen peroxide over zinc oxide @ zeolitic imidazolate Framework-8 composite catalysts

A promising method of producing hydrogen peroxide (H2O2) is the electrochemical two-electron water oxidation reaction (2e− WOR). In this process, it is important to design electrocatalysts that are both earth abundant and environmentally friendly, as well as offering high stability and production rates. The research of WOR catalysts, such as the extensively used transition metal oxides, is mainly focused on the modification of transition metal elements. Few studies pay attention to the protective heterostructure of metal oxides. Here, we demonstrate for the first time an organometallic skeleton protection strategy to develop highly stable WOR catalysts for H2O2 generation. Unlike the pure ZnO and zeolite imidazole framework-8 (ZIF-8) catalysts, ZnO@ZIF-8 enabled the production of hydrogen peroxide at high voltages. The experimental results demonstrate that the ZnO@ZIF-8 catalyst stably generates H2O2 even under a high voltage of 3.0 V vs. RHE, with a yield reaching 2845.819 μmol/min g−1. ZnO@ZIF-8 shows a relatively low overpotential, with a current density of 10 mA cm−2 and an overpotential of 110 mV. The ZnO@ZIF-8 catalyst’s maximal FE value was 4.72 %. Moreover, the ZnO@ZIF-8 catalyst exhibits remarkable durability even after an extended 60-hour stability test. Operando Raman and theoretic calculation analyses reveal that the metal–organic skeleton being encapsulated on the metal oxide surface synergizes with each other, not only expanding the electrochemical surface area, but also adjusting the catalyst metal sites’ adsorption capacity. A novel approach to the modification of 2e− WOR metal oxide catalyst is presented in this work.

Tandem Fields Facilitating Directional Carrier Migration in Van der Waals Heterojunction for Efficient Overall Piezo-synthesis of H2O2.

Piezo-synthesis of H2O2 utilizing sustainable mechanical energy as well as earth-abundant water and oxygen is a green, cost-effective and promising approach. However, achieving simultaneous two-electron water oxidation reaction (2e- WOR) and two-electron oxygen reduction reaction (2e- ORR) faces huge challenges due to insufficient synergistic active sites and slow/messy carrier transfer. Herein, a novel 2D/2D van der Waals (vdW) heterojunction consisting of BiOIO3 and carbon nitride (BIO/CN) was elaborately designed for highly efficient overall H2O2 piezo-synthesis. Theoretical/experimental results revealed that a Z-scheme electron transfer was formed and facilitated by the tandem interfacial electric field and the bulk piezo-polarization field. On this basis, the carriers are efficiently separated while the oxidation/reduction capacity is preserved, thus providing strong driving force for the 2e- WOR and 2e- ORR on BIO and CN, respectively. Furthermore, the kinetic and thermodynamic process of WOR and ORR for H2O2 synthesis improved remarkably. Therefore, BIO/CN exhibits an excellent H2O2 yield of 259.8 μM within 30min in pure water and air atmosphere (without any sacrificial agents and aeration). This study provides a new idea on strategically controlling electron transfer towards high-efficiency H2O2 piezo-synthesis and expands the avenue for developing effective environmental purification materials. This article is protected by copyright. All rights reserved.

Photocatalytic H2O2 production and fuel cell performance based on PDI nanobelts enhanced by surface plasmon resonance of gold nanoparticles

The photocatalytic hydrogen peroxide (H2O2) fuel cell represents an innovative self-powered apparatus amalgamating the production and conversion of H2O2 to supply electricity. Using efficient photocatalyst as photoanode to realize two-electron water oxidation to produce H2O2 is considered as a key factor to improve the performance of fuel cell. In this study, perylene imide nanobelts decorated with gold nanoparticles (Au/PDI) were synthesized and subsequently employed as the photoanode to construct a photocatalytic H2O2 fuel cell. This cell can produce H2O2 under irradiation and store it, subsequently utilizing the stored H2O2 to generate electricity in the absence of light. The maximum power density of Au/PDI-based cell could reach 1.07 mW·cm−2 under AM 1.5 G solar light, which has around 1.7 times enhancement compared to PDI-based cell. Meanwhile, a specific capacitance of 5661 mF·cm−2 was obtained after 3 h irradiation. After operating the cell for 12 h, the specific capacitance remained at 50.2 % of its initial value. It is indicated that PDI-based photocatalysts hold considerable promise in water oxidation for H2O2 production. The incorporation of noble nanometals has shown effective enhancement in photocatalytic H2O2 production through the localized surface plasmon resonance (LSPR) effects, thereby enriching the photoanode materials designed for H2O2 fuel cell application.

Bioinspired Tetranuclear Manganese Cubane Complex as an Efficient Molecular Electrocatalyst for Two-Electron Water Oxidation Towards Hydrogen Peroxide.

Stable homogeneous two-electron water oxidation electrocatalysts are highly demanded to understand the precise mechanism and reaction intermediates of electrochemical H2O2 production. Here we report a tetranuclear manganese complex with a cubane structure which can electrocatalyze water oxidation to hydrogen peroxide under alkaline and neutral conditions. Such a complex demonstrates an optimal Faradaic efficiency (FE) of 87 %, which is amongst (if not) the highest FE(H2O2) of reported homogeneous and heterogeneous electrocatalysts. In addition, active species were identified and co-catalysts were excluded through ESI-MS characterization. Furthermore, we identified water binding sites and isolated one-electron oxidation intermediate by chemical oxidation of the catalyst in the presence of water substrates. It is evident that efficient proton-accepting electrolytes avoid rapid proton building-up at electrode and substantially improve reaction rate and selectivity. Accordingly, we propose a two-electron catalytic cycle model for water oxidation to hydrogen peroxide with the bioinspired molecular electrocatalyst. The present work is expected to provide an ideal platform to elucidate the two-electron WOR mechanism at the atomic level.

Characterization and H2O2 production mechanisms study on self-oxidized graphite during the two-electron water oxidation electrochemical process

The 2e− water oxidation process is an eco-friendly way to produce H2O2 using water as the raw material. It avoids the low solubility of oxygen in water, unlike traditional oxygen reduction methods. However, electrocatalysts always suffer from self-oxidation during the oxidation reaction, leading to decreased activity. We solved this by using non-metal graphite electrocatalysts that undergo an evolution process to oxidized carboxylated graphite, which is even more active. A defect forms on the graphite surface that facilitates HCO3− adsorption. The –COOH group easily forms a –COOOH intermediate, which is advantageous for hydrogen peroxide generation. The hydrogen peroxide generation rate is 4.55 times higher than that of initial graphite. Graphite is an environmentally friendly catalyst that avoids the release of metal ions, making it more suitable for large-scale applications.

Nanostructured boron-doped diamond electrodes for two-electron water oxidation to produce hydrogen peroxide

Boron-doped diamond (BDD) electrodes have been widely used in water treatment, e.g., degradation of antibiotics and pigments for water purification. Hydrogen peroxide production by two-electron electrochemical oxidation of water is a green and attractive method that has the potential to replace the conventional anthraquinone autoxidation (AO) process. In this study, BDD films were prepared on single-crystal silicon wafers by using hot-filament chemical vapor deposition (HFCVD) technique. Then, dense tubular nanostructure (nanotubes) arrays were prepared on the BDD films employing inductively coupled plasma (ICP) etching. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) proved the formation of oxygen-terminated nanostructures, which was ascribed to the oxygen plasma and the self-masking. The length of diamond nanotubes as well as the root diameter increased gradually and non-linearly with the increase of etching time. It was indicated by cyclic voltammetry (CV) analysis that the effective active area of the electrodes increased after etching, and variations of resulting reaction performance were observed. The oxygen-terminated and nanostructured BDD electrode obtained by etching with the optimized parameters features better electrocatalytic performance, with reduced oxidation potential and 46.8 % higher Faraday Efficiency (FE) for hydrogen peroxide production, compared to the original BDD sample. Therefore, the manufacturing of nanostructures is an effective method to improve the efficiency of BDD water oxidation for the production of hydrogen peroxide.

Carbazole-containing covalent triazine frameworks for efficient hydrogen peroxide photosynthesis from natural sunlight

Hydrogen peroxide (H2O2) photosynthesis via polymer photocatalysts is an environmentally friendly and sustainable method for H2O2 production. However, their efficiency is currently unsatisfactory due to limited dissociation and insufficient migration of photogenerated charge carriers. Constructing donor–acceptor (D-A) type polymer photocatalysts has been demonstrated to be a promising approach to improve their optical and electronic properties related to charge carrier separation and migration. Herein, we design two donor–acceptor (D-A) type carbazole-containing covalent triazine frameworks (CTF-PCZs), namely CTF-BPCZ and CTF-TPCZ. These CTF-PCZs are found to reduce the exciton binding energy (Eb) and enhance charge carriers transfer ability compared to non-D-A type CTF-HUST-1. Remarkably, CTF-TPCZ exhibit excellent H2O2 photosynthesis performance, achieving a rate of up to 10331 μmol g−1 h−1 from pure water under solar simulator (AM 1.5G), and 6039 μmol g−1 h−1 from pure water under natural sunlight irradiation in scaled-up photocatalytic experiments, significantly surpass those of all previously reported polymer-based photocatalysts. In-situ experiments provide direct evidence for intermediates involved in the photocatalytic process. Both experiments and DFT calculations reveal that the triazine ring fragment plays a crucial role in H2O2 photosynthesis through a two-step single-electron oxygen reduction reaction (ORR) and the carbazolyl group plays a crucial role in one-step two-electron water oxidation reaction (WOR).

Study on Influence Factors of H2O2 Generation Efficiency on Both Cathode and Anode in a Diaphragm-Free Bath.

Electrosynthesis of H2O2 via both pathways of anodic two-electron water oxidation reaction (2e-WOR) and cathodic two-electron oxygen reduction reaction (2e-ORR) in a diaphragm-free bath can not only improve the generation rate and Faraday efficiency (FE), but also simplify the structure of the electrolysis bath and reduce the energy consumption. The factors that may affect the efficiency of H2O2 generation in coupled electrolytic systems have been systematically investigated. A piece of fluorine-doped tin oxide (FTO) electrode was used as the anode, and in this study, its catalytic performance for 2e-WOR in Na2CO3/NaHCO3 and NaOH solutions was compared. Based on kinetic views, the generation rate of H2O2 via 2e-WOR, the self-decomposition, and the oxidative decomposition rate of the generated H2O2 during electrolysis in carbonate electrolytes were investigated. Furthermore, by choosing polyethylene oxide-modified carbon nanotubes (PEO-CNTs) as the catalyst for 2e-ORR and using its loaded electrode as the cathode, the coupled electrolytic systems for H2O2 generation were set up in a diaphragm bath and in a diaphragm-free bath. It was found that the generated H2O2 in the electrolyte diffuses and causes oxidative decomposition on the anode, which is the main influent factor on the accumulated concentration in H2O2 in a diaphragm-free bath.

Oxygen vacancy based WO3/SnO2-x promote electrochemical H2O2 accumulation by two-electron water oxidation reaction and toxic uniform dimethylhydrazine degradation

The key to constructing an anodic electro-Fenton system hinges on two pivotal criteria: enhancing the catalyst activity and selectivity in water oxidation reaction (WOR), while simultaneously inhibiting the decomposition of hydrogen peroxide (H2O2) which is on-site electrosynthesized at the anode. To address the issues, we synthesized novel WO3/SnO2-x electrocatalysts, enriched with oxygen vacancies, capitalize on the combined activity and selectivity advantages of both WO3 and SnO2-x for the two-electron pathway electrocatalytic production of H2O2. Moreover, the introduction of oxygen vacancies plays a critical role in impeding the decomposition of H2O2. This innovative design ensures that the Faraday efficiency and yield of H2O2 are maintained at over 80 %, with a noteworthy production rate of 0.2 mmol h−1 cm−2. We constructed a novel electro-Fenton system that operates using only H2O as its feedstock and applied it to treat highly toxic uniform dimethylhydrazine (UDMH) from rocket launch effluent. Our experiments revealed a substantial total organic carbon (TOC) removal, achieving approximately 90 % after 120 mins of treatment. Additionally, the toxicity of N-nitrosodimethylamine (NDMA), a byproduct of great concern, was shown to be effectively mitigated, as evidenced by acute toxicity evaluations using zebrafish embryos. The degradation mechanism of UDMH is predominantly characterized by the advanced oxidative action of H2O2 and hydroxyl radicals, as well as by complex electron transfer processes that warrant further investigation.

Rational engineering WO3-X/CNTs@carbon fiber membrane for the high-efficient produce H2O2 via electrochemical two-electron water oxidation route

The electrochemical two-electron water oxidation reaction (2e-WOR) offers a promising avenue for hydrogen peroxide (H2O2) production. It is crucial to design electrocatalysts with high selectivity, yield, resource abundance, and environmental friendliness. In this paper, as a new generation 2e-WOR electrocatalyst, the WO3-X/CNTs@carbon fiber membrane nanostructure with abundant oxygen-rich vacancy (OV) has been discovered by a series of test techniques including XRD, FE-SEM, TEM, FT-IR, Raman and XPS, comprising interconnected carbon nanotubes and carbon fibers enveloped in WO3 nanorods with oxygen-rich vacancies. By comparing the specific surface area of WO3-x/CNTs@carbon fiber membrane at different temperatures, it was observed that the maximum value is 44.09 m2/g when the mass ratio of AMT to PAN was 3:2 at 600 °C. Furthermore, the WO3-X/CNTs@carbon fiber membrane can be directly utilized as an independent electrode. The electrochemical performance test revealed that the Faraday efficiency of the WO3-X/CNTs @CF-600-2 can reach 54 % (2.48 V vs RHE (reversible hydrogen electrode)), while the H2O2 yield can achieve 10.3 μmol· min−1·cm−2, nearly ten times higher than that of pure WO3. Furthermore, the stability testing demonstrated that after 12 h, the WO3-X/CNTs @CF-600-2 exhibited excellent stability with minimal change in its Faraday efficiency. This enhancement is attributed to the improved selectivity of WO3, excellent electrical conductivity, and mass transfer performance of carbon fiber. Finally, we proposed a mechanism for 2e-WOR and provided some perspectives on this reaction along with summarizing recent discoveries.

Factors Controlling the Photochemical Two-Electron Water Oxidation Initiated By One-Electron in the Molecular Catalyst Sensitized System for Artificial Photosynthesis

Factors Controlling the Photochemical Two-Electron Water Oxidation Initiated By One-Electron in the Molecular Catalyst Sensitized System for Artificial Photosynthesis

Efficient Photosynthesis of Hydrogen Peroxide by Cyano-Containing Covalent Organic Frameworks from Water, Air and Sunlight.

The insufficient exciton (e- -h+ pair) separation/transfer and sluggish two-electron water oxidation are two main factors limiting the H2 O2 photosynthetic efficiency of covalent organic frameworks (COFs) photocatalysts. Herein, we present an alternative strategy to simultaneously facilitate exciton separation/transfer and reduce the energy barrier of two-electron water oxidation in COFs via a dicyano functionalization. The in situ characterization and theoretical calculations reveal that the dicyano functionalization improves the amount of charge transfer channels between donor and acceptor units from two in COF-0CN without cyano functionalization to three in COF-1CN with mono-cyano functionalization and four in COF-2CN with dicyano functionalization, leading to the highest separation/transfer efficiency in COF-2CN. More importantly, the dicyano group activates the neighbouring C atom to produce the key *OH intermediate for effectively reducing the energy barrier of rate-determining two-electron water oxidation in H2 O2 photosynthesis. The simultaneously enhanced exciton separation/transfer and two-electron water oxidation in COF-2CN result in high H2 O2 yield (1601 μmol g-1 h-1 ) from water and oxygen without using sacrificial reagent under visible-light irradiation. COF-2CN can effectively yield H2 O2 in water with wide pH range, in different real water samples, in scaled-up reactor under natural sunlight irradiation, and in continuous-flow reactor for consecutively producing H2 O2 solution for water decontamination.

"B" site-modulated perovskite oxide materials for efficient electrochemical water oxidation to hydrogen peroxide

Two-electron water oxidation (2e− WOR) has emerged as a promising method for H2O2 synthesis. However, achieving catalyst’ stability for hydrogen peroxide (H2O2) production through 2e− WOR under harsh oxidative conditions remains a significant challenge. Perovskite oxide catalysts have shown potential at low currents, but their electrocatalytic activity diminishes at high current densities. In this study, we successfully fabricated highly efficient 2e− WOR electrocatalysts by carefully selecting suitable B site metals with optimal O* and OH* adsorption characteristics. Our results demonstrate that the LaCoO3 catalyst exhibit exceptional H2O2 production rates, reaching 2977.29 μmol min−1 g−1. Furthermore, the LaCoO3 catalysts demonstrate remarkable durability and stable electrochemical performance even after an ultra-long 120-hour stability test. Density Functional Theory calculations (DFT) further demonstrate that we successfully screened catalysts that are thermodynamically more favorable at a 2e− WOR pathway and accelerate the rate-determining step of OH* to H2O2 by B-site modulation. This work presents a simple and effective strategy for designing perovskite catalysts tailored for efficient 2e− WOR.

(Invited) Metal Oxide Mixed Sulphide of Controlled Crystal Structure As Catalysts for Two-Electron Water Oxidation

Conventional catalysts based on noble metals (Pt, Ru) are often used for production of oxygen during water electrolysis in four-electron pathway as they can decrease gas evolution overpotential. Another possible valuable product from water oxidation is hydrogen peroxide obtained via two-electron process. Currently, transition metal oxides, are readily employed to catalyse this reaction. Although they display certain activity, it is still not satisfactory for mass production of H2O2, therefore further optimisations are needed. We suggest in this work, in addition to typical nanostructure modifications of metal oxides (MoO2) such as doping or structural engineering, an application of transition metal dichalcogenides (MoS2). Consequently, the oxide is partially replaced by sulphur. The selection of molybdenum as a centre atom ensures sufficient electrical conductivity of material as an electrode active layer. This combination is intended to provide the benefits thanks to layered materials of tuned interlayer spacing as well as controlled number of active sites. It enables selective adsorption of intermediate products of water oxidation (O∗, OH∗, and OOH∗), and therefore increased preference towards two-electron pathway.Various chemical approaches are considered to synthesize this material, especially hydrothermal treatment in autoclave and high-temperature sintering of precursors. The catalytic activity of the nanostructured metal oxide is further enhanced by its deposition on conductive high surface area support made of carbon/graphite particles of strictly defined textural parameters and surface chemistry. The final composite is obtained using hydrophobic binders (PVDF and PTFE) to form the electrode and improve the catalyst stability. The measurements are carried out in flow electrolyser unit with an alkaline electrolyte. The amount of produced H2O2, H2 as well as quantity and quality of evolved gases are assessed in terms of faradaic efficiency, pressure and overvoltage measurements.

The Nexus of Innovation: Electrochemically Synthesizing H2O2 and Its Integration with Downstream Reactions.

Hydrogen peroxide (H2O2) represents a chemically significant oxidant that is prized for its diverse applicability across various industrial domains. Recent innovations have shed light on the electrosynthesis of H2O2 through two-electron oxygen reduction reactions (2e- ORR) or two-electron water oxidation reactions (2e- WOR), processes that underscore the attractive possibility for the on-site production of this indispensable oxidizing agent. However, the translation of these methods into practical utilization within chemical manufacturing industries remains an aspiration rather than a realized goal. This Perspective intends to furnish a comprehensive overview of the latest advancements in the domain of coupled chemical reactions with H2O2, critically examining emergent strategies that may pave the way for the development of new reaction pathways. These pathways could enable applications that hinge on the availability and reactivity of H2O2, including, but not limited to the chemical synthesis coupled with H2O2 and waste water treatment byFenton-like reactions. Concurrently, the Perspective acknowledges and elucidates some of the salient challenges and opportunities inherent in the coupling of electrochemically generated H2O2, thereby providing a scholarly analysis that might guide future research.

Flower-like WO2@C prepared from the pyrolyzation of ionic liquid for effective elctrocatalytic two-electron water oxidation

Flower-like tungsten dioxide@carbon (WO2@C) is prepared through the pyrolysis of 1-octyl-3-methylimidazolium tungstate ionic liquids. The resultant WO2 particles are surrounded by a few of carbon fibers, displaying the unique flower-like morphology. The WO2@C testified efficient electrocatalytic activity for two-electron water oxidation reaction (2e- WOR) to H2O2. The electrocatalytic H2O2 production rate reaches about 6.55 μmol min−1 cm−2, over 2 times higher than WO2. This may be ascribed to the enhanced electron transferring capacities and abundant defects of WO2@C. This work introduces a special ionic liquid-derived metal oxide@C with the improved electrocatalytic activity for 2e- WOR.

Tuning the Selectivity and Activity of Graphite for the Two-Electron Water Oxidation Reaction via Doping with Heteroatoms: A Density Functional Theory Study

Tuning the Selectivity and Activity of Graphite for the Two-Electron Water Oxidation Reaction via Doping with Heteroatoms: A Density Functional Theory Study

Photocatalytic degradation of chlorinated organic pollutants by ZnS@ZIF-8 composite through hydrogen peroxide generation by activating dioxygen under simulated sunlight irradiation

Photocatalytic hydrogen peroxide (H2O2) production and its application in advanced oxidation processes (AOPs) are regarded as low-cost and environmentally friendly wastewater treatment processes. Herein, by modifying a small amount of sulphide on the zeolitic imidazolate framework-8 (ZIF-8), a ZnS@ZIF-8 composite and used for photocatalytic H2O2 production to degrade chlorinated organic pollutants under simulated sunlight (SSL). ZnS@ZIF-8 composite could enhance the separation of photo-induced charge carriers, promote electron transfer from zinc sulphide (ZnS) to ZIF-8, which exhibited good selectivity for the two-electron oxygen reduction reaction (2e--ORR) and two-electron water oxidation (2e--WOR) pathways. Based on oxygen (O2) activation, the developed ZnS@ZIF-8/O2/SSL system could achieve 6.43 mmol/L H2O2 production within 150 min, which was approximately 8.66 and 10.36 times higher than that of the ZnS/O2/SSL and ZIF-8/O2/SSL systems, respectively. In the ZnS@ZIF-8/O2/SSL system, the ORR, WOR and H2O2 photolysis led to the generation of hydroxyl radical (•OH), while the photochemical behavior of ZnS in ZnS@ZIF-8 composite resulted in the generation of active hydrogen (*H). Benefitting from the high concentration of H2O2 and the coexistence of redox species in the ZnS@ZIF-8/O2/SSL system, various chlorinated organic pollutants could be dechlorinated and mineralized. In addition, a possible mechanism for photocatalytic H2O2 production was also proposed. Importantly, the proposed process did not involve an additional sacrificial agent or Fenton-like catalysts. This work provides insights into the potential application of ZnS@ZIF-8 composite for H2O2 production and wastewater treatment.

A general strategy to enhance hydrogen peroxide generation via two-electron water oxidation by antimony modification for removal of triethyl phosphate and hexavalent chromium

Two-electron water oxidation has attracted more and more attention for H2O2 production. This strategy mainly uses water and does not require bubbling of oxygen gas, which can be widely used in oxygen-deficient environments. Currently, the most important research for two-electron water oxidation is the design of high-efficiency anode materials. Herein, a general method is developed to enhance the activity of two-electron water oxidation for H2O2 production via Sb2O3 modification. This strategy is suitable for a series of electrodes, including carbon fiber paper, graphite plate, WO3, CuWO4 and WO3&CuWO4 composite. The mechanism for Sb2O3 modification toward enhanced H2O2 generation is clearly demonstrated. It should be due to three factors: 1) enhance the reaction kinetic, 2) enlarge the specific surface area and 3) suppress H2O2 decomposition. According to density function calculation, it is firstly found that the Sb optimizes the Gibbs free energy of adsorbed *OH intermediate of its nearby atom, making its adjacent atom (such as W) the active site. Finally, these Sb-modified electrodes are firstly used to produce H2O2 for high-efficiency removal of triethyl phosphate, an environmental pollutant that are difficult to be degraded. It can also be used for the removal of hexavalent chromium, one kind of heavy metal.

Super-Oxidizing Covalent Triazine Framework Electrocatalyst for Two-Electron Water Oxidation to H2O2.

Electrochemical two-electron water oxidation (2e WOR) is gaining surging research traction for sustainable hydrogen peroxide production. However, the strong oxidizing environment and thermodynamically competitive side-reaction (4e WOR) posit as thresholds for the 2e WOR. We herein report a custom-crafted covalent triazine network possessing strong oxidizing properties as a proof-of-concept metal-free functional organic network electrocatalyst for catalyzing 2e WOR. As the first-of-its-kind, the material shows a maximum of 89.9% Faradaic Efficiency and 1428 μmol/h/cm2 H2O2 production rate at 3.0 V bias potential (vs reversible hydrogen electrode, RHE), which are either better or comparable to the state-of-the-art electrocatalysts. We have experimentally confirmed a stepwise 2e WOR mechanism which was further computationally endorsed by density functional theory studies.